Sturm says the double-title bout is the biggest of his career, even eclipsing his famous clash with legendary Oscar de la Hoya in Las Vegas eight years ago.

"Daniel Geale is a great great fighter. He's fast, he has a great jab and we're very excited about this fight," Sturm said on Fox Sports.

Geale's trainer Graham Shaw said his 31-year-old charge continued to improve.

"Without a doubt he (Sturm) is Daniel's most difficult opponent so far, but having said that Daniel improves every fight and I'd say he has improved 20 per cent from his last fight," Shaw told AAP from Germany.

"He's always in the gym. We're constantly working on different things. We talk a lot about tactics and things we need to do.

"Of course we've studied Felix but we can't spend too much time on that. We've got to worry about what we've got to do rather than 'he does this, we'd better do that'.

"We want to get him into that frame of mind that 'this is not meant to happen' and upset his rhythm.

"Do things that maybe Daniel Geale hasn't done before, that he hasn't seen on tape.

"Daniel Geale is a thinking fighter, so is Felix Sturm, but I'm sure there will be things that happen in the fight that they both have to respond to that's not in the game plan.

"For sure, you will certainly see things from Daniel Geale this fight you probably haven't seen before."

Spies will find it hard to learn anything about Geale, who thanks to a helpful gym owner in Essen is training behind locked doors.

Shaw said Geale was in the shape he wanted him to be just a few days out from the fight and his charge was looking sharper each day.